Differential ionic analyzer



June 17, 1947.

' R.- v. SEAMAN 2,422,264

DIFFERENTIAL IONIC ANALYZERS Filed May 8,, 1945 INVENTOR.

P051597 M -5AMAN.

BY I r Patenteditlune .17, 19 47 'UNITED STATE PATENT OFFICE This invention relates to mass spectrometry for determining the mass. abundance and character of the isotopes of elements and more particularly to a mass spectrometer or differential ionic analyzer which will divide the negative ions and fragments from the positive ions and fragments so that the mass and abundance of each may be determined simultaneously and independently'as differentiated from the usual spectrometer in which only the ions of one polarity are impinged againsta, single target or collector charged with the opposite polarity.

Another object of the invention is to provide an analyzer in which both quantitative electronic reactions of the ions and the spectroscopic analysis thereof can be made simultaneously and independently.

Other objects and advantages reside in the detail construction of the invention, which is designed for simplicity, economy, and efllciency. 'Ih'ese will become more apparent from the following description.

In the following detailed description of the invention, reference is had to the accompanying drawing which forms a part hereof. Like nu- .merals refer to lik parts in all views of the drawing and throughout the description.

The drawing diagrammatically illustrates the elements of the improved differential ionic analyzer. Briefly, the improved spectrometer or differential analyzer ionizes any desired element or angle of the targets is such as to reflect light combination of elements in either the gaseous,

liquid, or solid stages; divides the positive ions from the negative ions; and thence impinges the ions of one polarity upon one analyzing target and the ions of the opposite polarity upon a second independent target. The targets are each equipped with apparatus for making a complete ionic and spectrographic analysis of the ions of the respective polarities.

The above is accomplished by means of a Y-tube, in the stem of which the element or elements to be analyzed are received and ionized. The two legs of the Y.-tube terminate in target bulbs and are provided with means for attracting ions of opposite polarities respectively.

The Y-tube is constructed of any suitable material such as pyrex; glass. Th stem of the tube is divided into a feed chamber In and an ionization chamber II. The feed chamber I0 is separated ,trom the ionization chamber II by means of a valve l2. A gas or vapor feed tube l3 opens into the feed chamber I0 and is controlled by means of a suitable stopcock It. The extremity of the feed chamber In is closed'by means of a 2 feed cock I! and the extremity of th'e ionization chamber ll tefminates in a control valve l3.

Beyond the control valve [3, the tube is divided to form two flaring leg tubes which will be herein designated as the negative leg tube l1 and the positive leg tube ii. The tubes I1 and I8 terminat e in target bulbs l9 and 20, respectively. An evacuating nippje 35, controlled by means of a vacuum cook 36, dommugiicates with the interior of the tubes I l and i8. I

An ion receiving plate or target 21 is positioned within each of the bulbs l9 and 20- in axial alignment with the tubes l1 and I8, respectively. The

traveling along the axes of the tubes l1 and i8 through focusing lenses 22 and through spectrographic slits 23 to reflecting prisms 24. The light rays from the prisms 24 are fed to any desired photographic or spectrographic apparatus for determining the elemental nature of the ions.

An electrically heated vaporizing screen 25 is placed in the ionization chamber II. The screen may have any desired construction, such as a continuous folded length of resistance wire supplied with current through suitable conductors 26. The ionization chamber is also provided with one or more setsof electronic plates 21 and filaments 28 upon which controlled voltages may be impressed through suitable conductors 29. That portion of the ionization chamber containing the plates and filaments is surrounded by means of a magnetizing solenoid which will be herein desig nated the stem solenoid 30. The two tubes l1 and it are each surrounded by means of a pair of spaced magnetizing solenoids which will be herein designated th leg solenoids 3i and 32.

-Metallic beam concentrating sleeves 33 and 34 are axially positioned within the tubes l1 and i8 and within the solenoids 3i ,and 32,-respectively. The sleeves 34 are of smaller diameter than. the

' sleeves 33 for reasons to be later described.

The interior of each of the bulbs l9 and 20 is coated with an electrical conducting coating 31 connected with a ground lead 39. The ion collector or target 2l in the bulb I9 is connected through a negative conductor 38 with the negative terminal of any suitable direct current source having a controllable, variable potential up to say 15,000 volts. The target 2| in the bulb 20 is similarly connected through a positive conductor 43 with the positive terminal of the same or a similar source.

The apparatus is designed to handl either gases, liquids or solids. Gases are introduced through the gas inlet 13 and the stopcock M.

Solids and liquids are introduced through the feed cock l onto a tilting shelf H in the feed chamber. The shelf 4! can be released from the exterior in any desired manner such as through the medium of an electromagnet 42 acting on a retractable latch 40. I

Let us assume that a sample of material is to be ionically analyzed. The sample is placed on the shelf 4| and th valve l5 and stopcock are closed. The valves I2 and I8 are opened and the entire interior of the Y-tube is evacuated through the vacuum nipple 35 to a pressure of, say 10- mm. Hg. After the evacuation has been completed, the cook 36 and the valve l6 are closed. The magnet 42 is then energized to allow the shelf 4| to tilt allowing the sample of material to fall onto the hot screen 25. The hot screen immediately vaporizes and partially ionizes the sample. This vapor is further ionized by bombardment of the stream of electrons being emitted by the first filament 28 accelerated by a potential of from 70 to 100 volts and thence by a second and more intense bombardment from the electrons of the second filament 2B accelerated by a still higher potential on the order of 1000 to 3000 volts. Direct current is being simultaneously supplied to the solenoid 30 so that the liberated ions are immersed in a strong magnetic field, which affects an ionic rotation and centrifugal separation thereof in consequence of their differences of electronic mass.

The valve I6 is now opened and the beam of spiraling ions is drawn to the entrances of the two leg tubes l1 and la. The negatively charged target 2| in the bulb l9 exerts a strong attraction for the positive ions in the beam and similarly repels the negative ions. target 2| in the bulb acts reversely and attracts the negative ions so that the ions in the beam are separated and divided at this point according to their individual polarities.

The concentrating sleeves 33 and 34 in the leg tubes are charged with the same polarity as the ions flowing therethrough, that is, the sleeves in the tube I! are positively charged and the sleeves in the tube I8 are negatively charged. They therefore act to repel the passing ions into compact axial cores or beams before they strike their respective targets. This regimentation and control of the flow of the ions is assisted by the centrifugal efiect produced by the magnetic fields of the solenoids 3| and 32. By control of the relative potentials on the targets and the concentrating sleeves and the currents feeding the solenoids, absolute control of the ion beams is attained.

The ions in the beams strike their respective targets where they are still further ionized and impress a potential on the target in accordance with their masses and abundance as in the usual electrometer. In this case, however, due to the preliminary division of the ions each target re ceives only the ions of one polarity.

Each of the ion collectors or targets II is connected through the medium of a conductor 33 or 43 with any suitable electronic detector tube to amplify any current impulses received due to the impingement of the ions on the targets 2| and feed them to suitable amplifying circuits. The current from the amplifying circuits is measured by any sensitive electronic method or is fed to a galvanometer (not shown) which deflects through an angle proportional to the abundance of the ions in each beam. The resulting deflections may be recorded in any desired manner, such as pho- The positively charged record of the given sample. The lighter ions will.

of course, attain greater velocity than the heavier ones and will strike the targets first followed by the successively heavier ions. Since the voltage developed is a characteristic of the velocity the resulting curve developed will give a differentiation between individual classes of ions.

By control of the vacuum and the impressed potential the stream of ions can be made to glow with ionic light. The beams therefore assume the nature of light beams and the light therefrom is reflected by the targets through the lenses 22 and the slits 23 to any suitable spectrograph where the spectrum of the ions may be studied and/or recorded. Thus, a spectrographic qualitative analysis ofthe divided beams can be made simultaneously with the electronic quantitative analysis.

If desired, the targets may be activated with a fluorescent coating, in which case fluorescent light will be admitted by the impact of the ions and this light will be focused through the lenses 22 and the slits 23 for analysis, consideration, of course, being given to the effect of the fluorescent coating on the resulting spectrum.

Another way in whichwthe light may be produced is by the ionization of impact of the ions on the target which may also be used for spectrographic analysis.

Stray ions outside of the beam strike the conducting coating 31 in the bulbs and their charges are dissipated through the ground leads 39.

In the above described method of operation, a single evacuation of the tubes is described. It may be desirable in some cases to allow the vacuum pump to operate continuously so as to evacuate excess vapors and gases which may be formed.

The Y-tube may be cleaned out after an experiment or operation in any desired manner. One method is to fully vaporize any substances which have been introduced and withdraw them through the evacuating nipple as a vapor. After use on gases, the tubes may be flushed with nitrogen and the latter evacuated by suction.

While a specific formof the improved analyzer has been diagramed and described herein together with suggested circuits for obtaining the necessary electrical results, it is to be understood that these are only suggestive and that the methods and means for producing the desired currents and potentials form no part of the present invention.

Having thus described the invention, what is claimed and desired secured by Letters Patent is:

1. A differential ionic analyzer comprising: an ionization chamber; a negative tube extending from said chamber; a positive tube extending from said chamber; a negatively charged ion target at the extremity of the negative tube for attracting positive ions; and a positively charged ion target at the extremity of the positive tube V for attracting negative ions.

2. A differential ionicanalyzer comprising: an ionization chamber; a negative tube extending from said chamber; a. positive tube extending from said chamber; a negatively charged ion target at the extremity of the negative tube for attracting positive ions; a positively chargedion target at the extremity of the positive tube for attracting negative ions; and indicating means in conjunction with each target to independently indicate the characteristics of the ions impinged upon each target.

3. A difierential ionic analyzer comprising: a feed chamber; means for sealing said feed chamber from the atmosphere; an ionization chamber; valve means for placing said two chambers in communication; a heating element in said ionization chamber for vaporizing a sample to be analyzed; a negative tube extending from said ionization chamber; a positive tube extending from said ionization chamber, each of said tubes terminating in a target bulb; a negative ion target in the bulb at the extremity of the negative tube; a positive ion target in the bulb'at the extremity of the positive tube; and electronic means for indicating the ionic impingement'on each of said targets.

4. A differential ionic analyzer comprising: a feed chamber; means for sealing said feed chamber from the atmosphere; an ionization chamber;

valve means for placing said two chambers in communication; a heating element in said ionization chamber for vaporizing a sample to be ana lyzed; an electron emitting element in said ionization chamber for bombarding the vapor therein;

' a negative tube extending from said ionization chamber; a positive tube extending from said ing in a target bulb; a negative ion target in the bulb at the extremity of the negative tube; a positive ion target in the. bulb at the extremity of the positive tube; and electronic means for indicating the ionic impingement on each of said targets.

v5. A difierential ionic analyzer comprising: a feed chamber; means for sealing said feed chamber from theatmosphere; an ionization chamber; valve means for placing said-two chambers in communication; a heating element in said ionization chamber for vaporizing a sample to be analyzed; a negative tube extending from said ionization chamber; a positive tube extending from said ionization chamber, each of said tubes terminating in a target bulb; a negative ion target in the bulb at the extremity of the negative tube; a positive ion target in the bulb at the extremity of the positive tube; electronic means for indicating the ionic impingement on each of said targets; and a solenoid surrounding said ionization chamber for imparting rotation to the ions there- 6. A differential ionic analyzer comprising: a feed chamber; means for sealing said feed chamber from the atmosphere; an ionization chamber;

valve means for placing said two chambers in communication; a heating element in said ionization chamber for vaporizing a sample to be analyzed; a negative tube extending from said ionization chamber; a positive tube extending from said ionization chamber; each of said tubes terminatingv in a target bulb; a negative ion target in,

the bulb at the extremity of the negative tube; a positive ion target in the bulb at the extremity of the positive tube; electronic means for indicating the ionic impingement on each of said targets; and a metallic focusing sleeve in each of said tubes, said sleeves being charged with a polarity corresponding to that of the ions flowing in that tube. I I

'7. A differential ionic analyzer comprising: an ionization chamber; a negative tube extending ionization chamber, each of said tubes terminatfrom said chamber; a positive tube extending attracting negative ions; and means for receiving light reflected from said targets.

8. A differential ionic analyzer comprising: an ionization chamber; a negative tube extending from said chamber; a positive tube extending 9; A differential ionic analyzer comprising: a

feed chamber; means for sealing said feed chamber from the atmosphere; an ionization chamber; valve means for placing said two chambers in communication; a heating element in said ionization chamber for vaporizing a sample to be analyzed;'a negative tube extending from said ionization chamber; a positive tube extending from said ionization chamber, each of saidtubes terminating in a target bulb; a negative ion targetinthe bulb at the extremity of the negative tube;, a positive ion target in the bulb at the extremity of the positive tube; electronic means for indicating the ionic impingement on each of said targets; a' sample receiving shelf in said feed. chamber';"and I I means for causing said shelf to deposit the re-, 30

ceived sample on said heating element. l

" 10. A differential ionic analyzer comprising:

a feed chamber; means for sealing said feed chamber from the atmosphere; an ionization chamber; valve means for placing said two ch'ambers in communication; a heating element in said ionization chamber for vaporizing a sample to be analyzed; a negative tube extending from said ionization chamber; a positive tube extending from said ionization chamber, each of said tubes terminating in a target bulb; a negative ion target in the bulb at the extremity of the nega-- v tive tube; a positive ion target in the bulb at the I extremity of the positive tube; electronic-means for indicating the-ionic impingement on each of said targets; means for introducing a gas into said j' gases feed chamber; and means for evacuating from all of said'chambers and tubes.

11. A diiferential ionic analyzer comprising? a stem tube; means for introducing a sampleto be analyzed into said st'm tube; an ionization chamber formed in said stem tube; a negative leg tube extending from said stem tube; a positive leg tube extending from said stem tube; a target bulb formed on the extremity of each leg tube; means for evacuating all of said tubes; an ion target positioned within each of said bulbs in axial alignment with its respective leg tubes; a focusing lens positioned in optical alignment with each of said tangets; means for impressing a positive electrical charge on the target in the positive tube; and means for impressing a negatarget bulb formed on the extremity of each leg tube; means for evacuating all of said tubes; an ion target positioned within each of said bulbs in axial alignment with its respective legtube; a focusing lens positioned in optical alignment with each of said targets; means for impressing a positive electrical charge on the target in the positive leg tube; means for impressing a negative electrical charge on the target in said negative leg tube; and an independent spectrographic apparatus receiving the light from each of said lenses for determining the elemental nature of the ions in each bulb.

13. A ditlerential ionic analyzer comprising: a stem tube; means for introducing a sample to be analyzed into said stem tube; an ionization chamber-formed in said stem tube; a negative leg tube extending from said stem tube; a positive leg tube extending from said stem tube; a target bulb formed on the extremity of each leg tube; means for evacuating all of said tubes; an ion target positioned within each of said bulbs in axial alignment with its respective leg tube; means for impressing a positive electrical charge on the target in the positive leg tube; means for impressing a negative electrical charge on the target in said negative leg tube; an electrically heated vaporizing grid in said stem tube; ionizing means in said stem tube; and indicating means operable in consequence of the impingement of ions on said targets.

14. A difierential ionic analyzer comprising; a stem tube; means for introducing a sample to be analyzed into said stem tube; an ionization chamber formed in said stem tube; a negative leg tube extending from said stem tube; a positive leg tube extending from said stem tube; a target bulb formed on the extremity of each leg tube; means for evacuating all of said tubes; an ion target positioned within each of said bulbs in axial alignment with its respective leg tube; means for impressing a positive electrical charge on the target in the positive leg tube; means for impressing a negative electrical charge on the target in said negative leg tube; an electrically heated vaporizing grid in said stem tube; ionizing means in said stem tube; indicating means operable in consequence of the impingement of ions on said targets; an electrically energized solenoid surrounding said stem tube; and similar solenoids surrounding the two leg tubes for imparting ionic rotation to the ions therein.

15. A difierential ionic analyzer comprising: a stem tube; means for introducing a sample to be analyzed into said stem tube; an ionization chamber formed in said stem tube; a negative leg tube extending from said stem tube; a positive'leg tube extending from said stem tube; a target bulb formed on the extremity of each le tube; means for evacuating all of said tubes; an ion target positioned within each of said bulbs in axial alignment with its respective leg tube; means for impressing a positive electrical charge on the target in the positive leg tube; means for impressing a negative electrical charge on the target in said negative leg tube; an electrically heated vaporizing grid in said stein tube; ionizing means in said stem tube; indicating means operable in consequence of the impingement of ions on said targets; tubular. metallic, beam concentrating sleeves axially positioned within each of said leg tubes, said sleeves being charged with an electrical polarity corresponding to that of the charge of the ions flowing through the respective tubes.

16. A differential ionic analyzer comprising: a stem tube; means for introducing a sample to be analyzed into said stem tube; an ionization chamber formed in said stem tube; a. negative leg tube extending from said stem tube; a positive leg tube extending from said stem tube; a,

target bulb formed on the extremity 01 each leg tube; means for evacuating all of said tubes; an

ion target positioned within each of said bulbs in axial alignment with its respective leg tube; means. for impressing a positive electrical charge on the target in the positive leg tube; means for impressing a negative electrical charge on the target in said negativ leg tube; an electrically heated vaporizing grid in said stem tube; ionizing means in said stem tube; indicating means operable in consequence of the impingement of ions on said targets; an electrical conducting lining within each of said bulbs for collecting stray ions; and means for carrying oil the charge from said lining.

ROBERT V. SEAMAN.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name Date 917,191 Trivelli Apr. '6, 1909 2,341,551 Hoover Feb. 15, 1944 

